In the art of boring into the earth with a drill string, particularly for oil and gas production, the drill string periodically becomes lodged within a subsurface formation. Failure to release the frozen drill pipe can result in an abandonment of the well. In response, spotting fluids were developed to lubricate the affected area, "spotting" referring to the placement of a quantity of drilling fluid known as a pill or slug containing a release agent at the area of concern. Furthermore, incorporating a lubricating factor into the drilling mud during ordinary operation to prevent drill pipe sticking is a common practice.
The composition of these release agents has generally consisted of various kinds of oils such as synthetic oils, vegetable oils, mineral oils, diesel oils and crude oils. Oil-based spotting fluids, however, are generally difficult to prepare because strong agitation is required to achieve an oil-water suspension taking much time when time may be a crucial consideration.
Disposal of drilling fluids containing oil components has also come under much closer environmental scrutiny and regulation concurrent with increasing concern about reducing pollutants in ground water and coastal water environs. Drilling muds containing oil are generally classified as pollutant streams having costly regulated disposal procedures. Such oils are not in the best interest of marine wild life and may leave an unsightly sheen in the water.
Accordingly, there is an urgent need for a spotting fluid release agent and lubricant in the art of oil and gas production which is nontoxic, non-oil based, inexpensive and easy to prepare and use. The Applicant has no knowledge of the prior use of an aqueous-based composition comprising glycerophosphoric acid esters and diacetyltartaric acid esters of mono and/or diglycerides in the petroleum industry as a spotting fluid and lubricant.
U.S. Pat. No. 4,876,017 discloses a composition of matter comprising a synthetic hydrocarbon compound such as a poly-.alpha.-olefin which may be combined with emulsifiers and thinners to serve as a downhole lubricant. The lubricant is said to be nontoxic to marine life. The poly-.alpha.-olefin may also function as a spotting fluid.
Preparation of glycerophosphoric acid ester in its various isomeric forms is disclosed in several articles including, Cherbuliez et al., Helv. Chim. Acta, vol. 29, p. 2006 (1946), Baer et al., Journal of Biological Chemistry, vol. 128, p. 491 (1939), and Baer et al., Journal of Biological Chemistry, vol. 135, p. 321 (1940).